Description:Melocactus curvispinus is highly variable in shape, it has has been divided into several species and subspecies by hobbyists, but only 3 subspecies are valid (subsp. curvispinus, subsp. caesius and subsp. dowsonii).Habit: Usually solitary.Stem: Depressed globular to short cylindrical, light to dark green, slightly glaucous, 8 to 27 cm in diameter, 6 to 30 cm tall. Ribs: 10 to 16 ribs sharp and sometimes tuberculated. Areoles: Slightly sunken in the notches.Spines: Dirty white to almost black more or less curved. Central spines erect, 1 to 4 often missing, 15 to 52 mm long. Radial spines 6 to 11 (rarely more), 3-42 mm long, the lowest often longer. Cephalium: Relatively small 3 to 4 cm tall and 7 to 11 cm in diameter with long reddish-brown bristles.Flowers: From the cephalium, dark purple to light pink, 18 to 43 mm long and 10 to 25 mm in diameter.Blooming season: spring to summer open late in the afternoon. Fruit: Club-shaped, pink to bright red to deep magenta slightly lighter at the base.subspecies by hobbyists, but only 3 subspecies are valid.

Subspecies, varieties, forms and cultivars of plants belonging to the Melocactus curvispinus group

Melocactus curvispinusPfeiff.: Subsp. curvispinus has radial spines that curve backwards strongly, about 28 mm in length. Distribution: widespread in Mexico, Central America, Colombia and western Venezuela up to of 1500 meters of altitude.

Melocactus curvispinus subs. caesius(H.L.Wendl.) N.P.Taylor: has radial spines that are practically straight and 28 mm (or more) long. Distribution: Caribbean, coastal areas of Colombia and Venezuela at an altitude up to 700 meters

Melocactus guitartiiLeón: it is about 10 cm broad and 12 cm high, densely armed with long spreading rigid spines. Distribution: Arroyo Blanco next to the lake of Manaquitas, Sancti Spiritus, Cuba.

Notes: The most remarkable part of a Melocactus is its cephalium a bristle-coated structure on the summit of the plant, only Melocactus , and the similar genus Discocactus possesses this type of permanent, apical, hatlike appendage. It’s only when a Melocactus reaches maturity that the cephalium begins to grow. Cylindrical, with a diameter distinctly smaller than that of the plant body below, the cephalium will keep growing for the rest of the plant’s life, but the body of the plant stops growing the moment the cephalium starts to form. As the plants age the cephalium doesn’t increase in circumference it will steadily grow taller.

Cultivation and Propagation: These cacti are not the easiest things to grow and aren’t plants for beginners. Melocactus guaricensis grows from April to October, it can’t endure long stretches of total dryness, and also too much water will rot it, as its weak root systems tends to be inefficient at sucking up water from wet soil. Nonetheless, again as a result of their tropical origins, they need a fair amount of water, but allow the soil to dry quite a bit before watering again.Melocactus rests from October to April but can’t stand cold, or even fairly cool temperatures, so is indispensable to keep it above 8-12°C at all times, severe damage or death occurring at temperatures that the great majority of cacti wouldn’t mind in the least and prefer more frequent water in winter than other cacti, say once a month. Do not feed in winter.The root system is weak and generally resents being repotted and can take a long time to re-establish. The soil mix should be very quick draining, prefers very bright light, not as much as the most arid growing cacti, but plenty nonetheless.Propagation: Exclusively by Seeds. Sow in February-march in a light, sandy, porous soil. Cover germinating tray with glass to prevent seed from drying out. Germination is most successful at a temperature of 18 to 22° C.